Microwave antenna having a coaxial cable with an adjustable outer conductor configuration

ABSTRACT

A microwave ablation system includes a power source. A microwave antenna is adapted to connect to the power source via a coaxial cable that includes inner and outer conductors having a compressible dielectric operably disposed therebetween. The inner conductor in operative communication with a radiating section associated with the microwave antenna. The outer conductor includes a distal end transitionable with respect to each of the inner conductor, compressible dielectric and radiating section from an initial condition wherein the distal end has a first diameter to a subsequent condition wherein the distal end has second diameter. Transition of the distal end from the initial condition to the subsequent condition enhances the delivery of microwave energy from the power source to the inner conductor and radiating section such that a desired effect to tissue is achieved.

CROSS-REFERENCE TO RELATED APPLICATION(S)

The present application is a continuation application of U.S. patentapplication Ser. No. 13/206,075 filed on Aug. 9, 2011, the entirecontents of which are incorporated by reference herein.

BACKGROUND

1. Technical Field

The present disclosure relates to microwave antennas. More particularly,the present disclosure relates to microwave antennas having a coaxialcable with an adjustable outer conductor configuration.

2. Background of Related Art

Microwave ablation procedures, e.g., such as those performed formenorrhagia, are typically done to ablate the targeted tissue todenature or kill the tissue. Many procedures and types of devicesutilizing electromagnetic radiation therapy are known in the art. Suchmicrowave therapy is typically used in the treatment of tissue andorgans such as the prostate, heart, and liver.

One non-invasive procedure generally involves the treatment of tissue(e.g., a tumor) underlying the skin via the use of microwave energy. Themicrowave energy is able to non-invasively penetrate the skin to reachthe underlying tissue. Typically, microwave energy is generated by apower source, e.g., microwave generator, and transmitted to tissue via amicrowave antenna that is fed with a coaxial cable that operably couplesto a radiating section of the microwave antenna.

To enhance energy delivery efficiency from the microwave generator tothe microwave antenna, impedance associated with the coaxial cable, theradiating section and/or tissue need to equal to one another, i.e., animpedance match between the coaxial cable, the radiating section and/ortissue. In certain instances, an impedance mismatch may be presentbetween the coaxial cable, the radiating section and/or tissue, and theenergy delivery efficiency from the microwave generator to the microwaveantenna is compromised, e.g., decreased, which, in turn, may compromisea desired effect to tissue, e.g., ablation to tissue.

SUMMARY

The present disclosure provides a microwave ablation system. Themicrowave ablation system includes a power source. A microwave antennais adapted to connect to the power source via a coaxial cable thatincludes inner and outer conductors having a compressible dielectricoperably disposed therebetween. The inner conductor in operativecommunication with a radiating section associated with the microwaveantenna. The outer conductor includes a distal end transitionable withrespect to each of the inner conductor, compressible dielectric andradiating section from an initial condition wherein the distal end has afirst diameter to a subsequent condition wherein the distal end hassecond diameter. Transition of the distal end from the initial conditionto the subsequent condition enhances the delivery of microwave energyfrom the power source to the inner conductor and radiating section suchthat a desired effect to tissue is achieved.

The present disclosure provides a microwave antenna adapted to connectto a power source for performing a microwave ablation procedure. Themicrowave antenna includes inner and outer conductors having acompressible dielectric operably disposed therebetween. The innerconductor in operative communication with a radiating section associatedwith the microwave antenna. The outer conductor includes a distal endtransitionable with respect to each of the inner conductor, compressibledielectric and radiating section from an initial condition wherein thedistal end has a first diameter to a subsequent condition wherein thedistal end has second diameter. Transition of the distal end from theinitial condition to the subsequent condition enhances delivery ofmicrowave energy from the power source to the inner conductor andradiating section such that a desired effect to tissue is achieved.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of the presentdisclosure will become more apparent in light of the following detaileddescription when taken in conjunction with the accompanying drawings inwhich:

FIG. 1 is a schematic view of a microwave ablation system adapted foruse with a microwave antenna that utilizes a coaxial cable with anadjustable outer conductor configuration according to an embodiment ofthe present disclosure;

FIG. 2A is partial, cut-away view of a distal tip of the microwaveantenna depicted in FIG. 1 illustrating the coaxial cable with theadjustable outer conductor configuration coupled to a radiating sectionassociated with microwave antenna;

FIG. 2B is a cross-sectional view taken along line segment “2B-2B”illustrated in FIG. 2A;

FIG. 2C is partial, cut-away view of an alternate distal tip designillustrating a coaxial cable with the adjustable outer conductorconfiguration coupled to a radiating section associated with microwaveantenna according to an alternate embodiment of the present disclosure;

FIG. 3A is an enlarged view of the area of detail 3A depicted in FIG.2A;

FIG. 3B is a side view of a coaxial cable depicted in FIG. 3A with atransitional distal end of an outer conductor shown in a compressedcondition;

FIGS. 4A-4B are side views of an alternate embodiment of the coaxialcable depicted in FIGS. 3A and 3B with a transitional distal end of anouter conductor shown in noncompressed and compressed conditions,respectively;

FIGS. 5A-5B are side views of an alternate embodiment of the coaxialcable depicted in FIGS. 3A and 3B with a transitional distal end of anouter conductor shown in noncompressed and compressed conditions,respectively; and

FIGS. 6A-6B are side views of yet another embodiment of the coaxialcable depicted in FIGS. 3A and 3B with a transitional distal end of anouter conductor shown in noncompressed and compressed conditions,respectively.

DETAILED DESCRIPTION

Embodiments of the presently disclosed system and method are describedin detail with reference to the drawing figures wherein like referencenumerals identify similar or identical elements. As used herein and asis traditional, the term “distal” refers to the portion which isfurthest from the user and the term “proximal” refers to the portionthat is closest to the user. In addition, terms such as “above”,“below”, “forward”, “rearward”, etc. refer to the orientation of thefigures or the direction of components and are simply used forconvenience of description.

Referring now to FIGS. 1-2C, and initially with reference to FIG. 1, amicrowave ablation system in accordance with an embodiment of thepresent disclosure is designated system 10. A microwave antenna 12operably couples to generator 100 including a controller 200 thatconnects to the generator 100 via a flexible coaxial cable 14. In thisinstance, generator 100 is configured to provide microwave energy at anoperational frequency from about 300 MHz to about 10 GHz. Microwaveantenna 12 includes a distal radiating portion or section 16 that isconnected by a feedline or shaft 18 to coaxial cable 14. Microwaveantenna 12 couples to the cable 14 through a connection hub 26. Theconnection hub 26 includes an outlet fluid port 28 and an inlet fluidport 30 connected in fluid communication with a sheath or cannula 32.Cannula 32 is configured to circulate coolant fluid 33 from ports 28 and30 around the antenna assembly 12 via respective fluid lumens 34 and 35(FIG. 2A). Ports 28 and 30, in turn, couple to a supply pump 38. For amore detailed description of the microwave antenna 12 and operativecomponents associated therewith, reference is made to commonly-ownedU.S. Pat. No. 8,118,808 filed on Mar. 10, 2009.

With reference to FIGS. 2A-3B, and initially with reference to FIG. 2A,a coaxial cable 14 configuration according to an embodiment of thepresent disclosure is shown. Coaxial cable 14 extends from the proximalend of the microwave antenna 12 and includes an inner conductor 20 thatis operably disposed within the shaft 18 and in electrical communicationwith a distal radiating section 16 (FIGS. 1 and 2A). Coaxial cable 14includes a compressible dielectric 22 and an outer conductor 24 havingan adjustable distal end 25 surrounding each of the inner conductor 20and compressible dielectric 22. A portion of the coaxial cable 14 ismovable in one or more directions to cause the distal end 25 totransition from a noncompressed condition to a compressed condition,described in greater detail below.

As noted above, an impedance mismatch may be present between a coaxialcable and a radiating section associated with conventional microwaveantennas. As a result thereof, the energy delivery efficiency from themicrowave generator to the microwave antenna may be compromised, e.g.,decreased, which, in turn, may compromise a desired effect to tissue,e.g., tissue ablation. More particularly, impedance associated with themicrowave antenna 12 varies over the course of an ablation cycle due to,for example, tissue complex permittivity changes caused by temperatureincrease. That is, because the ablated tissue is in a “near field” ofthe microwave antenna 12, the ablated tissue essentially becomes part ofthe microwave antenna 12. The impedance changes cause an increase inreflective power back to the generator 100 and reduce energy depositsinto tissue.

In accordance with the present disclosure, a length of the coaxial cable14 is configured for tuning (i.e., impedance matching) an impedanceassociated with the inner conductor 20, outer conductor 24 and tissue ata target tissue site such that an optimal transfer of electrosurgicalenergy is provided from the generator 100 to the radiating section 16such that a desired tissue effect is achieved at a target tissue site.More particularly, the distal end 25 associated with the outer conductor24 is adjustable, e.g., transitionable, adjacent an antenna feed point,i.e., adjacent the radiating section 16, to compress the compressibledielectric 22 and alter the ratio between the outer conductor 24 and theinner conductor 20, see FIG. 3A in combination with 3B.

Referring to FIG. 3A, coaxial cable 14 includes inner conductor 20 thatis configured similar to conventional inner conductors. Moreparticularly, inner conductor 20 is made from one or more conductivematerials, e.g., copper, and is substantially encased by a dielectric,e.g., compressible dielectric 22, see FIG. 2B, for example. A portion ofthe inner conductor 20 operably couples to the radiating section 16 byone or more suitable coupling methods. Inner conductor 20 serves as aconductive medium that transfers electrosurgical energy from thegenerator 100 to the radiating section 16. More particularly, a distalend 21 of the inner conductor extends past a feed point start (e.g.,past outer conductor 24 and compressible dielectric 22, see FIG. 2C incombination with FIG. 3A) and couples to the radiating section 16 (seeFIGS. 1 and 2A, for example). Typically, during initial transmission ofelectrosurgical energy from the generator 100 to the radiating section16, the impedance present at the distal end 21 of the inner conductor 20and the radiating section 16 is approximately equal to 50Ω (i.e., thecharacteristic impedance of the coaxial cable 14), as best seen in FIG.3A. It should be noted that this 50Ω impedance is at least partially theresult of the ratio of the diameter of the outer conductor 24 comparedto the diameter of the inner conductor 20.

Compressible dielectric 22 is operably disposed between the outerconductor 24 and inner conductor 20 and, as noted above, substantiallyencases the inner conductor 20. Compressible dielectric 22 may be madefrom any suitable dielectric material that is capable of being deformedor compressed. Suitable material that compressible dielectric 22 may bemade from includes but is not limited to electrical insulation paper,relatively soft plastics, rubber, etc. In certain embodiments,compressible dielectric 22 is made from polyethylene that has beenchemically, or otherwise, treated to provide a degree ofcompressibility. In other instances, the compressible dielectric 22 maybe made from polytetrafluoroethylene (PTFE), air, etc. Compressibledielectric 22 extends along a length of the coaxial cable 14. In theillustrated embodiment, compressible dielectric 22 extends partiallyalong a portion of the coaxial cable 14 that is operably disposed withinthe microwave antenna 12. In certain embodiments, it may prove useful toprovide the entire length of the coaxial cable with the compressibledielectric 22. Compressible dielectric 22 is deformable from aninitially noncompressed condition to a compressed condition when thedistal end 25 of the outer conductor 24 transitions from an initial,noncompressed, condition to a, subsequent, compressed condition; thesignificance of which is described in greater detail below. A distal endof the compressible dielectric 22 (the distal end of the compressibledielectric 22 is encased by the distal end 25 of the outer conductorand, as a result thereof, is not explicitly shown) defines a feed pointstart.

With continued reference to FIG. 3A, outer conductor 24 may be made fromany suitable conductive material, e.g., a material having a generallyrigid configuration, such as, for example, a pair of coaxially disposedcircumferential sheets of copper. More particularly, outer conductor 24includes a fixed outer conductor 24 a and a movable or translatableouter conductor jacket or sleeve 24 b (“outer sleeve 24 b”). Fixed outerconductor 24 a and outer sleeve 24 b are disposed in electricalcommunication with one another. A portion, e.g., a distal end 40, of thefixed outer conductor 24 a operably couples to the distal end 25. Moreparticularly, distal end 40 of fixed outer conductor 24 a is configuredto support the distal end 25 such that the distal end 25 may transitionfrom the noncompressed condition to the compressed condition. With thispurpose in mind, the distal end 40 of the fixed outer conductor 24 a maysecurely couple to the distal end 25 by one or more suitable coupling orsecurement methods. For example, in the illustrated embodiment, distalend 40 of fixed outer conductor 24 a operably couples to the distal end25 via one of soldering, welding and brazing. In certain embodiments,distal end 25 may be monolithically formed with the fixed outerconductor 24 a. Fixed outer conductor 24 a supports translatable outersleeve 24 b such that outer sleeve 24 b may translate or rotatethereabout. In certain embodiments, one or more lubricious materials maybe operably disposed between an external surface (not explicitly shown)of the fixed outer conductor 24 a and an internal surface (notexplicitly shown) of the outer sleeve 24 b. For example, one or moresuitable oils or waxes may be operably disposed between the externalsurface of the fixed outer conductor 24 a and the internal surface ofthe outer sleeve 24 b. Alternatively, or in combination therewith, oneor both of the external surface of the fixed outer conductor 24 a andthe internal surface of the outer sleeve 24 b may be made from amaterial that has a low coefficient of friction, e.g., a material suchas, Delron, Torlon, PTFE, etc. Fixed outer conductor 24 a is configuredsuch that fixed outer conductor 24 a remains in a substantially fixedorientation when the outer sleeve 24 b is translated thereabout.Accordingly, when outer sleeve 24 b is translated (or in some instancesrotated) about fixed outer conductor 24 a, outer sleeve 24 b and fixedouter conductor 24 a remain in electrical communication with oneanother.

Distal end 25 is transitionable with respect to each of the innerconductor 20, outer conductor 24 including fixed outer conductor 24 aand outer sleeve 24 b, compressible dielectric 22 and radiating section16. More particularly, the distal end 25 transitions from an initialcondition wherein the distal end 25 has a first diameter, to asubsequent condition wherein the distal end 25 has second diameter. Thatis, in a noncompressed condition, the distal end 25 includes a firstdiameter “D1” and when the distal end 25 is in a compressed conditionthe distal end 25 includes a second diameter “D2,” wherein the diameter“D2” is less than diameter “D1,” see FIG. 3A in combination with FIG.3B, for example.

In the embodiment illustrated in FIGS. 3A and 3B, distal end 25 is madefrom a conductive wire mesh or weave 25 a that is made from one or moresuitable conductive materials, e.g., a wire mesh or weave made fromcopper, silver, gold, stainless steel, titanium, nickel or combinationthereof. Wire mesh 25 a includes a generally cylindrical configurationwhen in a pre-transition condition and a generally frustoconicalconfiguration when in the post transition condition, as best seen inFIGS. 3A and 3B. The configuration of a wire mesh or weave 25 afacilitates transitioning from one condition to another while providingstructural integrity for the distal end 25. As noted above, the distalend 40 of the fixed outer conductor 24 a operably couples to the distalend 25. Likewise, a portion of the wire mesh 25 a operably couples tothe outer sleeve 24 b by one or more suitable coupling methods includingbut not limited to one or more mechanical interfaces (e.g., weaving aportion of the wire mesh with and/or into the outer sleeve 24 b), one ormore types of bonding agents (e.g., epoxy adhesives), or other suitablecoupling method. In the illustrated embodiment, a pair of loose proximalends 29 couple and/or form part of the wire mesh or weave 25 a andoperably couple to the outer sleeve 24 b via a heat cure adhesive,soldering, brazing, welding, etc. Accordingly, when the outer sleeve 24b is moved, e.g., translated proximally, it “pulls” the proximal ends29, which, in turn, causes the wire mesh 25 a of the distal end 25 totransition or tighten to the compressed condition, which, in turn,causes the compressible dielectric 22 to deform or compress to thecompressed condition such that the diameter of the distal end 25transitions from diameter “D1” to diameter “D2.”

In accordance with the present disclosure, transitioning of the distalend 25 from the noncompressed condition to the compressed conditionmaximizes delivery of microwave energy from the generator 100 to theinner conductor 22 and radiating section 16 such that a desired effectto tissue is achieved. To this end, outer sleeve 24 b is translatablerelative to the fixed outer conductor 24 a. As noted above, outer sleeve24 b operably couples to the distal end 25 of the outer conductor 24 andis configured such that proximal translation of the outer sleeve 24 brelative to the fixed inner conductor 24 a causes the distal end 25 totransition from the initial, noncompressed, condition to the subsequent,compressed condition. In the illustrated embodiment, the distance thatouter sleeve translates is equal to or corresponds to the decease of thediameter associated with the distal end 25. More particularly, for agiven amount of translation of outer sleeve 24 b the diameter of thedistal end 24 b will decrease (or in some instances increase)proportionately. For example, in certain embodiments, a 1:1 ratiobetween translation of the outer sleeve 25 b and transition of thedistal end 25 from the first diameter “D1” to the second diameter “D2”is utilized. That is, when the outer sleeve 24 b translates 0.001 inchesthe second diameter “D2” of the distal end 25 decreases 0.001 inchesfrom the original diameter “D1.” The ratio may be altered to achieve adesired impedance, tissue effect, ablation zone shape, etc. One skilledin the art can appreciate that other ratios may be utilized whenmanufacturing and/or assembling the coaxial cable 14.

A drive mechanism 50 is in electrical communication with generator 100via an electric circuit 60 (FIG. 1) and operably couples to outer sleeve24 b. More particularly, drive mechanism 50 is operably disposed withinmicrowave antenna 12 adjacent hub 26. Drive mechanism 50 includes one ormore components (e.g., a drive rod, servo, servo drives, or othersuitable device(s)) that are operably coupled to the outer sleeve 24 band configured to translate the outer sleeve 24 b proximally and, insome instances, distally. In certain instances, drive mechanism 50includes one or more components (e.g., a drive rod, servo, servo drives,or other suitable device(s)) that are operably coupled to the outersleeve 24 b and configured to rotate the outer sleeve 24 b, e.g., rotatethe outer sleeve 24 b in a clockwise and/or counterclockwise direction.

An outer plastic jacket or sheath 52 is operably disposed along a lengthof the coaxial cable 14. Sheath 52 functions similar to known sheathsthat are typically associated with coaxial cables and, as such, onlythose features that are unique to sheath 52 are described hereinafter.One or more of the lubricious materials described above may be operablydisposed between an internal surface of the sheath 52 and the externalsurface of the fixed outer conductor 24 a and/or outer sleeve 24 b.

In certain instances, sheath 52 (FIG. 2C) may operably couple to thedistal end 25 and may be configured to “pull” the wire mesh 25 a of thedistal end 25. More particularly, and in this instance, the outerconductor 24 includes a fixed conductor 24 a and does not include anouter sleeve 24 b. That is, the sheath 52 takes the place of the outersleeve 24 b. More particularly, the sheath 52 encases the fixed outerconductor 24 a and is operably coupled to and in operative communicationwith the drive mechanism 50 via the one or more of the previouslydescribed components.

In certain instances, one or more springs (not shown) may be operablyassociated with the wire mesh 25 a of the distal end 25. In thisinstance, the spring(s) may be configured to facilitate transitioningthe wire mesh 25 a. For example, in some instances, it may prove usefulor necessary to increase the impedance between the inner conductor 20and distal end 25 of the outer conductor 24. In this instance, the outersleeve 24 b may be configured for distal translation relative to thefixed outer conductor 24 a. That is, the outer sleeve 24 b may beconfigured to translate distally past the distal end 40 of the fixedouter conductor 24 a and toward the distal end 25 and/or radiatingsection 16 such that the wire mesh 25 a transitions from an unexpandedcondition to an expanded condition and the impedance between the innerconductor 20 and distal end 25 of the outer conductor 24 is increased.In this instance, the drive mechanism 50, and operative componentsassociated therewith, is configured to translate the outer sleeve 24 b(or in some instances, the sheath 52) distally.

In one particular embodiment, the controller 200 is configured toautomatically control operation of the operative components associatedwith the coaxial cable 14. More particularly, when the impedance of themicrowave antenna 12 requires adjustment, one or more modules, e.g.,coaxial adjustment control module 202 (FIG. 1), associated with thecontroller 200 commands electric circuit 60 to supply power to the drivemechanism 50 such that the outer sleeve 24 b may be actuated. In oneparticular embodiment, the controller 200 may be configured to determinea difference between forward and reflected power and determine a loadmismatch thereby causing electric circuit to activate the drivemechanism 50.

Operation of system 10 is now described. A portion of the microwaveantenna, e.g., a radiating section 16, is positioned adjacent a targettissue site. Initially, the diameter of the wire mesh 25 a isapproximately equal to “D1” that corresponds to an initialcharacteristic impedance “ZO” of the coaxial cable 14, e.g., animpedance “ZO” that is approximately equal to 50Ω. Thereafter,electrosurgical energy is transmitted from the generator 100 to theradiating section 16 of the microwave antenna 12 such that a desiredtissue effect may be achieved at the target tissue site. As theradiating portion 16 emits electromagnetic energy into tissue and thetissue desiccates, an impedance mismatch between the microwave antenna12 and tissue may be present at the target tissue site. To compensatefor this impedance mismatch, the outer sleeve 24 b (or in certaininstances, the sheath 52) is “pulled” proximally. The compressibledielectric 22 allows the wire mesh 25 a of the distal end 25 totransition, e.g., compress or tighten, under the pulling force providedby the outer sleeve 24 b. The wire mesh 25 a of the distal end 25 willto compress to a diameter that is approximately equal to “D2,” which, inturn, decreases the impedance and compensates for the impedancemismatch. In accordance with the present disclosure, the configurationof adjustable distal end 25 of the fixed outer conductor 24 a and innerconductor 20 improves electrosurgical energy transfer from the generator100 to the microwave antenna 12 and/or the target tissue site and allowsthe microwave antenna 12 or portion associated therewith, e.g.,radiating section 16, to be utilized with more invasive ablationprocedures.

With reference to FIGS. 4A and 4B an alternate embodiment of the coaxialcable 14 is shown designated 114. Coaxial cable 114 is substantiallysimilar to that of coaxial cable 14. As a result thereof, only thosefeatures that are unique to coaxial cable 114 are described in detail.

Coaxial cable includes an inner conductor 120, an outer conductor 124and a compressible dielectric 122 that surrounds the inner conductor120. A distal end 125 operably couples to a distal end 140 of the outerconductor 124 and is made from one or more suitable types of a shapememory alloy (e.g., Nitinol) that forms a wire mesh 125 a. Moreparticularly, shape memory alloys (SMAs) are a family of alloys havinganthropomorphic qualities of memory and trainability and areparticularly well suited for use with medical instruments. Nitinol whichcan retain shape memories for two different physical configurations andchanges shape as a function of temperature. SMAs undergo a crystallinephase transition upon applied temperature and/or stress variations. Aparticularly useful attribute of SMAs is that after it is deformed bytemperature/stress, it can completely recover its original shape onbeing returned to the original temperature. The ability of an alloy topossess shape memory is a result of the fact that the alloy undergoes areversible transformation from an austenite state to a martensite statewith a change in temperature (or stress-induced condition). Thistransformation is referred to as a thermoelastic martensitetransformation. Under normal conditions, the thermoelastic martensitetransformation occurs over a temperature range which varies with thecomposition of the alloy, itself, and the type of thermal-mechanicalprocessing by which it was manufactured. In other words, the temperatureat which a shape is “memorized” by an SMA is a function of thetemperature at which the martensite and austenite crystals form in thatparticular alloy.

Unlike the configuration of coaxial cable 14 depicted in FIGS. 3A and3B, the mesh 125 a does not rely on a “pulling” force to transition froma noncompressed condition to a compressed condition. More particularly,a pair of loose proximal ends 129 associated with the wire mesh 125 isin electrical communication with the generator 100 and/or one or moremodules associated with the controller 200. In this instance, thegenerator, or an operative component associated therewith, e.g.,electrical circuit 60, supplies current to the wire mesh 125 a such thatthe wire mesh 125 a may transition from a noncompressed condition, to acompressed condition, e.g., its original cold forged shape. Moreparticularly, as current is supplied, via the proximal ends 129, to thewire mesh 125 a, the current heats the wire mesh 125 a and causes thewire mesh 125 a to transition back to its (referring to the wire mesh125 a) cold forged shape, e.g., a distal end 125 having a generallyfrustoconical shape with a diameter approximately equal to “D2,” seeFIG. 4B, for example.

Operation of system 10 that includes a microwave antenna 12 with acoaxial cable 112 is now described. Only those operative features thatare unique to the microwave antenna 12 with a coaxial cable 112 aredescribed hereinafter.

To compensate for an impedance mismatch, electrical current is suppliedto the wire mesh 125 a such that current may resistively heat the wiremesh 125 a. Resistively heating the wire mesh 125 a causes the wire mesh125 a to transition back to the cold forged shape of the wire mesh 125a. The compressible dielectric 122 allows the wire mesh 125 a of thedistal end 25 to transition, e.g., compress or tighten, to a generallyfrustoconical shape with a diameter approximately equal to “D2,” which,in turn, decreases the impedance and compensates for the impedancemismatch. In accordance with the present disclosure, the configurationof adjustable distal end 125 of the outer conductor 124 and innerconductor 120 improves electrosurgical energy transfer from thegenerator 100 to the microwave antenna 12 and/or the target tissue siteand allows the microwave antenna 12 or portion associated therewith,e.g., radiating section 16, to be utilized with more invasive ablationprocedures.

With reference to FIGS. 5A and 5B an alternate embodiment of the coaxialcable 14 is shown designated 214. Coaxial cable 214 is substantiallysimilar to that of coaxial cable 14. As a result thereof, only thosefeatures that are unique to coaxial cable 214 are described in detail.

Coaxial cable includes an inner conductor 220, an outer conductor 224that includes a fixed outer conductor 224 a and a rotatable outer sleeve224 b, and a compressible dielectric 222 that surrounds the innerconductor 220. Outer sleeve 224 b is rotatably coupled to the fixedinternal outer conductor 224 a and wire mesh 225 a of distal end 225such that rotation of the outer sleeve 224 b causes wire mesh 225 a totransition from a noncompressed condition to a compressed condition. Inthe embodiment illustrated in FIGS. 5A and 5B, the outer sleeve 224 b isrotatably coupled to the fixed outer conductor 224 a by one or moresuitable mechanical interfaces. More particularly, one or more rampedthreads 201 are in mechanical communication with one or morecorresponding slots 203. For illustrative purposes, the ramped threads201 are shown operably disposed along an exterior surface of the fixedouter conductor 224 a and the corresponding slots 203 are shown operablydisposed along an interior surface of the outer sleeve 224 b. Thisconfiguration of ramped threads 201 and corresponding slots 203 ensuresthat clockwise rotation of the outer sleeve 224 b causes proximaltranslation of the outer sleeve 224 b, which, in turn, causes the wiremesh 225 a to transition from a noncompressed condition to a compressedcondition. Conversely, counterclockwise rotation of the outer sleeve 224b causes distal translation of the outer sleeve 224 b, which, in turn,causes the wire mesh 225 a to transition from the compressed conditionback to the noncompressed condition. While the present disclosuredescribes a configuration of a ramped threads 201 and correspondingslots 203 to facilitate rotation of the outer sleeve 224 b with respectto fixed outer conductor 224 a, it is within the purview of the presentdisclosure that one or more other methods or devices may be utilized toachieve the intended purposes described herein.

Distal end 225 operably couples to a distal end 240 of the fixed outerconductor 224 a in a manner as described above with respect to distalend 25 and distal end 24.

A pair of loose proximal ends 229 associated with the wire mesh 225 isoperably coupled to the outer sleeve 224 b such that rotation of outersleeve 224 b causes the wire mesh 225 a to transition from anoncompressed condition, to a compressed condition. Proximal ends 229may be coupled to the outer sleeve 224 b by one or more suitablecoupling methods, e.g., one or more coupling methods previouslydescribed above with respect to proximal ends 29.

A drive mechanism 50, configured in a manner as described above, is inoperable communication with the outer sleeve 224 b. More particularly,the drive mechanism 50 is configured to impart rotational motion of theouter sleeve 224 b such that the outer sleeve 224 b may translateproximally and, in some instances, distally.

To compensate for an impedance mismatch, the outer conductor (or incertain instances, the sheath 52) is rotated in a clockwise direction.The compressible dielectric 222 allows the wire mesh 225 a of the distalend 225 to transition, e.g., compress or tighten, under the rotationalor pulling force provided by the outer sleeve 224 b. The wire mesh 225 aof the distal end 225 will to compress to a diameter that isapproximately equal to “D2,” which, in turn, decreases the impedance andcompensates for the impedance mismatch. In accordance with the presentdisclosure, the configuration of adjustable distal end 225 of the outerconductor 224 and inner conductor 220 improves electrosurgical energytransfer from the generator 100 to the microwave antenna 12 and/or thetarget tissue site and allows the microwave antenna 12 or portionassociated therewith, e.g., radiating section 16, to be utilized withmore invasive ablation procedures.

With reference to FIGS. 6A and 6B an alternate embodiment of the coaxialcable 14 is shown designated 314. Coaxial cable 314 is substantiallysimilar to that of coaxial cable 14. As a result thereof, only thosefeatures that are unique to coaxial cable 314 are described in detail.

Coaxial cable includes a translatable inner conductor 320, an outerconductor 324 and a compressible dielectric 322 that surrounds the innerconductor 320. Unlike the inner conductors previously described, innerconductor 320 is configured to translate, e.g., proximally and/ordistally, relative to the outer conductor 324 and compressibledielectric 322. To this end, one or more lubricious materials describedabove may be operably disposed between the compressible dielectric 322and inner conductor 320 to facilitate translation of the inner conductor320.

An incompressible dielectric disk 323 (disk 323) of suitable proportionand having a suitable shape is operably disposed on (e.g., via one ormore suitable securement methods) and along a length of the innerconductor 320. Disk 323 is configured to “push” against a distal portionof the compressible dielectric 322 when the inner conductor 320 istranslated proximally such that the compressible material is caused tocompress or deform radially inward. To this end, disk 323 is ofsubstantially rigid construction including a generally circumferentialconfiguration having a diameter that is less than a predetermineddiameter, e.g., diameter “D2,” of a wire mesh 325 a when the wire mesh325 a is in a compressed state. Disk 323 may be made from any suitablematerial including but not limited those previously described herein,e.g., polyethylene.

Compressible dielectric 322 may be configured in a manner as previouslydescribed, e.g., compressible dielectric 22. In the embodimentillustrated in FIGS. 6A and 6B, compressible dielectric 322 is operablycoupled or secured to the wire mesh 325 a by one or more suitablecoupling or securement methods. More particularly, compressibledielectric 322 is secured to the wire mesh 325 via an epoxy adhesive.Accordingly, when the compressible dielectric 322 deforms or compresses,the wire mesh 325 a transitions to the compressed condition.

A drive mechanism 50, configured in a manner as described above, is inoperable communication with the inner conductor 320. More particularly,the drive mechanism 50 is configured to impart translation of the innerconductor 320 such that the inner conductor 320 may translate proximallyand, in some instances, distally.

Outer conductor 324 includes a distal end 325 that operably couples to adistal end 340 that forms a wire mesh 325 a.

To compensate for an impedance mismatch, inner conductor 320 includingdisk 323 is moved proximally relative to outer conductor 324 andcompressible dielectric 322. The compressible dielectric 322 pushesagainst the wire mesh 325 a of the distal end 325, this, in turn, causesthe wire mesh 325 a to transition, e.g., compress or tighten, under thepushing force against the compressible dielectric 322 provided by thedisk 323 and inner conductor 320. The wire mesh 325 a of the distal end325 will to compress to a diameter that is approximately equal to “D2,”which, in turn, decreases the impedance and compensates for theimpedance mismatch.

From the foregoing and with reference to the various figure drawings,those skilled in the art will appreciate that certain modifications canalso be made to the present disclosure without departing from the scopeof the same. For example, one or more modules associated with thegenerator 100 and/or controller 200 may be configured to monitor theimpedance at the target tissue site during the transmission ofelectrosurgical energy from the generator 100 to the microwave antenna12. More particularly, one or more sensors (e.g., one or more voltage,impedance, current sensors, etc.) may be operably positioned at apredetermined location and adjacent the radiating section 16 and/ortarget tissue site. More particularly, the sensor(s) may be operablydisposed along a length of the microwave antenna 12 and in operativecommunication with the module(s) associated with the generator 100and/or controller 200. The sensor(s) may react to or detect impedancefluctuations associated with the microwave antenna 12 and/or tissue atthe target tissue site during the ablation procedure. In this instance,the sensor(s) may be configured to trigger a control signal to themodule(s) when an impedance mismatch is present. When the module(s)detects a control signal, the module calls for power to be supplied toan electrical circuit that is in operative communication with the drivemechanism 50 such that the drive mechanism 50 actuates one or more ofthe operative components, e.g., outer sleeve 24 b, such that arespective wire mesh, e.g., wire mesh 25 a of distal end 25, is causedto transition from the noncompressed condition to the compressedcondition.

While several embodiments of the disclosure have been shown in thedrawings and/or discussed herein, it is not intended that the disclosurebe limited thereto, as it is intended that the disclosure be as broad inscope as the art will allow and that the specification be read likewise.Therefore, the above description should not be construed as limiting,but merely as exemplifications of particular embodiments. Those skilledin the art will envision other modifications within the scope and spiritof the claims appended hereto.

1. (canceled)
 2. A microwave antenna, comprising: a coaxial cableconfigured to be coupled to a power source, the coaxial cable including:an inner conductor; a radiating section in operative communication withthe inner conductor; an outer conductor; and a dielectric disposedbetween the inner and outer conductors, wherein at least a portion ofthe outer conductor is transitionable with respect to each of the innerconductor, the radiating section, and the dielectric.
 3. The microwaveantenna according to claim 2, wherein an impedance of the coaxial cableis adjusted by transitioning of the portion of the outer conductor. 4.The microwave antenna according to claim 2, wherein the portion of theouter conductor is transitionable between a first configuration and asecond configuration.
 5. The microwave antenna according to claim 4,wherein in the first configuration, the portion of the outer conductorhas a first dimension, and in the second configuration, the portion ofthe outer conductor has a second dimension.
 6. The microwave antennaaccording to claim 5, wherein the first dimension is a first diameterand the second dimension is a second diameter, the second diameter beingless than the first diameter.
 7. The microwave antenna according toclaim 4, wherein in the first configuration, the portion of the outerconductor is in a noncompressed configuration, and in the secondconfiguration, the portion of the outer conductor is in a compressedconfiguration.
 8. The microwave antenna according to claim 4, whereinthe dielectric is compressible such that thickness of the dielectricdecreases as the portion of the outer conductor transitions from thefirst configuration to the second configuration.
 9. The microwaveantenna according to claim 2, wherein the portion of the outer conductoris disposed at a distal end of the outer conductor.
 10. The microwaveantenna according to claim 2, wherein the outer conductor includes afixed segment and an outer sleeve operably coupled to the fixed segmentand translatable relative thereto, the outer sleeve being configuredsuch that proximal translation of the outer sleeve relative to the fixedsegment and the inner conductor causes the portion of the outerconductor to transition.
 11. The microwave antenna according to claim 2,wherein the portion of the outer conductor includes a wire mesh.
 12. Themicrowave antenna according to claim 2, wherein the portion of the outerconductor includes a shape memory alloy.
 13. The microwave antennaaccording to claim 12, wherein the portion of the outer conductor isoperably coupled to an electrical power source configured to resistivelyheat the portion of the outer conductor.
 14. The microwave antennaaccording to claim 2, wherein the outer conductor includes a fixedsegment and an outer sleeve operably coupled to the fixed segment andlongitudinally translatable relative thereto, the outer sleeve beingconfigured such that longitudinal translation of the outer sleeverelative to the fixed segment and the inner conductor causes the portionof the outer conductor to transition.
 15. The microwave antennaaccording to claim 14, wherein the portion of the outer conductor istransitionable from an initial, unexpanded condition to a subsequent,expanded condition.
 16. A coaxial cable configured to be coupled to apower source, the coaxial cable comprising: an inner conductor; aradiating section in operative communication with the inner conductor;an outer conductor; and a dielectric disposed between the inner andouter conductors, wherein at least a portion of the outer conductor isconfigured to be selectively transitionable between at least twoconfigurations.
 17. The coaxial cable according to claim 16, whereinimpedance of the coaxial cable is adjustable based on a configuration ofthe at least two configurations of the portion of the outer conductor.18. The coaxial cable according to claim 16, wherein the at least twoconfigurations includes a first configuration, in which the portion ofthe outer conductor has a first dimension, and a second configuration,in which the portion of the outer conductor has a second dimension. 19.The coaxial cable according to claim 18, wherein the first dimension isa first diameter and the second dimension is a second diameter, thesecond diameter being less than the first diameter.
 20. The coaxialcable according to claim 16, wherein the portion of the outer conductoris disposed at a distal end of the outer conductor.